Overview

A geological basin is an extensive depression in the Earth's crust where the surface sits relatively low compared with surrounding areas. Basins may be open to the ocean or isolated inland; many are located below modern sea level and can host marine or marginal marine environments.

How basins form

Basins develop for several reasons. Tectonic processes such as crustal stretching, flexural loading from mountain building, and thermal subsidence can create space that sinks and collects material. Local processes — for example, erosion that removes surrounding support or collapse over weakened rock — also produce depressions that function as basins. Over geological time these sinks continue to subside and accommodate increasing thicknesses of deposited material.

Sediment accumulation and geological records

Because basins act as natural traps for transported material, they are major sites of sediment accumulation. Rivers, wind, glaciers and the sea deliver particles that build layered sedimentary sequences. Inland basins share this role with lakes, which are the other common locations where sediments accumulate and are preserved. The strata preserved within basins record changes in environment and can be studied to infer the palaeoclimate of a surrounding continent and its evolution through time.

Types of basins (common categories)

  • Rift and extensional basins — formed where the crust is pulled apart.
  • Foreland basins — produced by flexure of the lithosphere adjacent to mountain belts.
  • Intracratonic basins — long-lived, broad depressions within continental interiors.
  • Sag or thermal subsidence basins — developed as the lithosphere cools and sinks.

Scientific and economic importance

The architecture and fill of basins are important to several fields. They are primary targets for oil and other hydrocarbon exploration because organic-rich, buried sediments can generate and trap hydrocarbons. Hydrologists study basins to understand aquifer systems and groundwater flow. Paleontologists and sedimentologists use basin deposits to reconstruct past ecosystems, climates and geological events.